RESUMO
Skin infections are frequently treated via intravenous or oral administration of antibiotics, which can lead to serious adverse effects and may sometimes contribute to the proliferation of resistant bacterial strains. Skin represents a convenient pathway for delivering therapeutic compounds, ensured by the high number of blood vessels and amount of lymphatic fluids in the cutaneous tissues, which are systematically connected to the rest of the body. This study provides a novel, straightforward method to obtain nafcillin-loaded photocrosslinkable nanocomposite hydrogels and demonstrates their performance as drug carriers and antimicrobial efficacy against Gram-positive bacteria. The novel formulations obtained, based on polyvinylpyrrolidone, tri(ethylene glycol) divinyl ether crosslinker, hydrophilic bentonite nanoclay, and/or two types of photoactive (TiO2 and ZnO) nanofillers, were characterized using various analytical methods (transmission electron microscopy (TEM), scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDX), mechanical tests (tension, compression, and shear), ultraviolet-visible spectroscopy (UV-Vis), swelling investigations, and via specific microbiological assays ("agar disc diffusion method" and "time-kill test"). The results reveal that the nanocomposite hydrogel possessed high mechanical resistance, good swelling abilities, and good antimicrobial activity, demonstrating a decrease in the bacteria growth between 3log10 and 2log10 after one hour of direct contact with S. aureus.
RESUMO
The present work investigates, for the first time, the synthesis and properties of some nanocomposite (NC) hydrogels obtained by the aqueous solution free radical polymerization of N-vinylpyrrolidone (NVP) in the presence of Laponite XLG (XLG) as a crosslinker, in comparison with the corresponding hydrogels prepared by using two conventional crosslinking divinyl monomers: N,N'-methylenebisacrylamide (MBA) and tri(ethylene glycol) divinyl ether (DVE). The structure and properties of the hydrogels were studied by FTIR, TEM, XRD, SEM, swelling and rheological and compressive mechanical measurements. The results showed that DVE and XLG are much better crosslinking agents for the synthesis of PNVP hydrogels than MBA, leading to larger gel fractions and more homogeneous network hydrogels. The hydrogels crosslinked by either DVE or XLG displayed comparable viscoelastic and compressive mechanical properties under the experimental conditions employed. The properties of the XLG-crosslinked hydrogels steadily improved as the clay content increased. The addition of XLG as a second crosslinker together with a divinyl monomer strongly enhanced the material properties in comparison with the hydrogels crosslinked by only one of the crosslinkers involved. The FTIR analyses suggested that the crosslinking of the NC hydrogels was the result of two different interactions occurring between the clay platelets and the PNVP chains. Laponite XLG displayed a uniform distribution within the NC hydrogels, the clay being mostly exfoliated. However, a small number of platelet agglomerations were still present. The PNVP hydrogels described here may find applications for water purification and in the biomedical field as drug delivery systems or wound dressings.
